The present invention generally relates to electrical connection boxes and more particularly, to an electrical connection box in which a peripheral wall of one of upper and lower casings is fitted into a peripheral wall of the other of the upper and lower casings and an engageable portion projecting from the upper casing or the lower casing is brought into engagement with a bracket mounted on a panel of a vehicle body such that the electrical connection box is not detached from the bracket even if external force is applied to the bracket by vibrations of the vehicle body, etc.
As shown in FIG. 1 and 2, a known electrical connection box such as a junction box used for connecting wiring harnesses for a motor vehicle to various electric devices includes upper and lower casings 2 and 3 having peripheral walls 2a and 3a, respectively and a locking claw 2b and a groove 3b are, respectively, formed on the peripheral walls 2a and 3a of the upper and lower casings 2 and 3. In a state where an internal circuit such as bus bars 1 is accommodated in the upper casing 2, the peripheral wall 2a of the upper casing 2 is fitted into the peripheral wall 3a of the lower casing 3 so as to be assembled with the peripheral wall 3a of the lower casing 3 such that the upper and lower casings 2 and 3 are locked to each other through engagement of the locking claw 2b of the upper casing 2 with the groove 3b of the lower casing 3. Meanwhile, as shown in FIG. 2, an engageable portion 3c is usually projected from the peripheral wall of the outer casing, i.e., the peripheral wall 3a of the lower casing 3 and is brought into engagement with a bracket 5 mounted on a panel 4 of a vehicle body.
In the known electrical connection box of the above described arrangement, when the panel 4 of the vehicle body is vibrated during running of the motor vehicle, external force is applied to the bracket 5 mounted on the panel 4 of the vehicle body, so that an engageable plate portion 5b of the bracket 5 is tilted about a fulcrum defined by a fixing portion 5a of the bracket 5 as shown in FIG. 3. As a result, the peripheral wall 3a of the lower casing 3 is pulled in the direction of the arrow of FIG. 3 through the engageable portion 3c held in engagement with the engageable plate portion 5b of the bracket 5 and thus, there is such a risk that the locking claw 2b of the upper casing 2 is disengaged from the groove 3b of the lower casing 3 as shown in FIG. 4.
Meanwhile, since the engageable portion 3c is provided on an outer face of the outer casing, large space is required to be provided at a portion of the vehicle body, on which the electrical connection box is mounted, so that space for installing the electrical connection box is increased and thus, it may be difficult to dispose the electrical connection box at a narrow site. Furthermore, if a guide 3d for receiving opposite side edges of the engageable plate portion 5b of the bracket 5 is provided on the lower casing 3, such a problem arises that the electrical connection box becomes larger in size.